Sewing machine



De@ 1129 3.950 G. SAUER v 29533940@ SEWING MACHINE Filed sept. ze, 194e s sheets-sheet 1 f GEORGE sAvER Dec., 12, E950 G. SAUER 2,533,400

ATPRNFIV G. SAUER SEWING MACHINE Dec., m9 1950 3 Sheets-Sheet 5 Filed Sept. 26, 1946 INVENTOR.

GEORGE SAUER ATTOB/VEY Patented Dec. l2, 1950 SEWING MAGHINE" George Sauer; Berwyn, Ill., assigner to Union Special Machine Company,v Chicago, 111:, acorporation oflllinois' Application September 26, 19.46, Serial No. 699566- 7Claim's; lY

The present invention relates to sewing machines and more particularly, to a-lubrication system especially adapted' to those' sewing machines having a rotary hook. ln such machines the provision oi means for lubricating the interengaging parts or" the rotary hook and the stationary bobbin assembly has presented a rather dilcult problem. It will be recognized that the provision of any excessive quantity, of oil may result in staining of the thread orV the throwing of oil on other'parts of the machine or possibly upon the' work. However, it is essential that an adequate and uniailing supply of oil be main# tained 'for the lubrication of the bearin'gsurfaces between' the rotary hook and the bobbin as seinl bly. These bearing surfaces comprise, in the machine to'be disclosed herein, a rib formed on one of 'the' parts of the'stationarybobbinvassembly and a .corresponding annular groove or raceway in the hooi; body. rThe hook body substantially surrounds the bobbin assembly andrsupports' the latter through the bearingl surfaces lust described. The bobbin assembly may include a bobbin case'and a' bobbin case holder and will be referred to herein as a bobbin casing. Thebobbin casing ls ordinarily' held against rotation by providing a' suitable. connection' between' the' bobbin 'case' holder' and theA frame' or base of the sewing machine. Since the'sp'eed of rotation of the` rotary hook irequ'ently reaches 10,000 R. P. M., it is apparent that the lubrication of this rather" extensive' and dicultly accessible bearing surface A-rnust'be carefully provided for.'

It an object 'of the present invention to'pro'- vide a lubricating system' for the rotaryhook of al sewing'ma'chine in which a constant, accuratelymetered supply ofoil is` positively con; ducted to'a passagewayl formed in thelh'ook shaft fromv which it may be conducted by' centrifugal force to the bearing surface between the rotary ingv device.. for supplying oil under'pressure'I is' drivenrby a shaft -rotatingl'at fa" decidedly slower' speedlthatithat of the' hook shaftwhereby 4'the' pressure fandV the quantity ofs olli supplied by such pumping means may not`bie excessive'and may' be simply and' easily adjusted. Other'andfu'ri ther Vobjects will in partV be app'arent and willin" shaft, hook j and bobbin casing? in' the" machinel Fig; l is a vertical 'sectiontaken along 'the 'line' iL-iloi Fig.' 2j .and

Figt isa detailed'sectional view 'ofthe pump; ing' mechanismin thei'machine 'sh'ownin Fig. 1;

Referring' now'to the drawings'and partieu IarlytO'Fig. 1, there is shown `aloclrstitc'zlfl sew'- ing' machine' ofi a type" to "which thefpresent'invention' isparticularly' adapted: The machine comprises'al base' generally indicatedat' l0; which may' comprise'a hollow casting: the4 upper 'sur'- face l2 of'which' serves`Y a's'the' clothfplatecf the machine'. TheflowerI portion ofI the" casting is closed as by a` plate lliandan oilsealingifgas` ket I E." Themachine is provided" with ah'ollow standard I8 which communicates with; certain of' the' hollow portions'of the"bas'e" and' which' may have integrally formedfth'er'ewth an" over'- han'gin'g, armZU'term'inating ina' head' 22."l

A'v main' drive'y shalt Ellextends through thearm 2) 'andhas fixed' at its`"righthan`d erro'l;v as viewed i'n'Fig. 1,'.a combined hand-'wheel'an'd' pulley 26 byirwhich the'mach'in'e maybe oper; ated 'manually or' by" power.' The shaft 2t ex-i tends into the head 22`ian'd`is connectedlwith" suitable mechanism therein' for vertical recipro# cation' of'aj needle' bar'itted atits' lower end with' a needle '36.`

lnthefupper portion of ythe .staar'lde'rdlil;v as shownin" Fig." 1, the 'shaft 24' has'xed" thereto a gear 32 meshing' With'ai"1'v idler gear* 3K5' which turn""mesh"es"with `a' gear" 3S Vxedto'a" shaft 38 extending'. generally longitudinally of 'the hol'- lowbase of` the machine. ReferringV now 't Fig. 2', it will be 'observedthat the'shaft 38 ismountd' for" rotation in a'suitable bearing dwcarried' by a web portion d2'of the base'ca'sting. At its left-y hand'enoftheshaft sa is rotatabiymountd inf'a; beanngneycarried'by theleftfw'all #trof thebasev cast-ing: The 4'shaft 38*y has formed therein"ad' jacent the wall 46 an eccentric or crank (not shown) with which cooperates an eccentric strap 48 forming a part of a telescopic pitman 50 having a hub 52 freely rotatable upon a suitable pivot (not shown) carried by a feed-rocker 54; The feed-rocker 54 also pivotally carries a hub S to which is connected a feed bar 58. Rotation of the shaft 38 is effective through the telescopic pitman 50 and a motion-modifying mechanism 6i) attached thereto to rock the feedrocker 5x2 and thus to impart horizontal motion to the feed-dog (not shown) carried by the feed bar 58.

The motion-modifying mechanism 60 has not been described in detail herein inasmuch as it is shown and described in full detail in U. S. Patent No. 2,035,508 granted March 3l, 1936 to Sauer et al. It should be pointed out that the motion-modifying mechanism 60 is so designed as to impart horizontal movements to the feeddog of adjustable extent whereby to vary the length of stitches produced by the machine.

Vertical movement is imparted to the feed bar 58 and through it to the feed-dog by means of a crank 52 formed upon the left-hand end of the shaft 38. The specific mechanism for connecting the crank 62 with the feed bar will not be described in detail herein inasmuch as a full description thereof is made in said U. S. Patent No. 2,035,508. The horizontal and vertical motions thus imparted to the feed-dog are such as to produce the four-motion feed normally employed in connection with a feed-dog in a sewing machine of this `general type.

l' 'The shaft 38 has fixed thereto a gear t4 which meshes with a gear 66 fixed to a rotary hook shaft 68. In view of the nature of the 'stitch formed by a machine of this type, it is necessary for the hook shaft to make two complete revolutions during the formation of a single stitch. The gear 64 is thus provided with twice the number of teeth provided on the gear 56. It is not at all unusual in the operation of a machine of the type disclosed herein for the machine to form approximately 5,000 stitches per minute and accordingly, the rotary hook shaft must rotate at approximately 10,000 R. P. M.

The right-hand end of the hook shaft, as viewed in Fig. 2, is mounted for rotation in a suitable bushing carried by a web portion 12 of the base casting. An elongated bushing 14 is carried in a lug portion 'It of the base casting as well as in the left wall 4S thereof. The bushing 'I4 extends from the gear 66 through the casting portions aforesaid and substantially into contact with a thrust collar 78 secured to the hook shaft. The bushing 14, together with the gear 66 and thrust collar i8 thus serves to prevent enwise motion of the hook shaft 68. At its left-hand end the hook shaft 63 has formed thereon an enlarged head 80 upon which the rotary hook (not shown in Fig. 2) is mounted.

Referring now to Fig. 3, the rotary hook is generally indicated at 82 and is shown in positionvupon the head B0 of the hook shaft 68. The rotary hook 82 has a recess 8d formed therein within which is received a bobbin casing 86. The bobbin casing 8E is provided with a projecting portion 88 which is engaged with a suitable device fixed to the frame of the machine whereby the bobbin casing 8S is held against rotation with the rotary hook 82. It will be understood that the engagement between the projecting portion 88 and the device which holds the bobbin casing 8E against rotation allows for a small amount of play thereby providing for slight movement of the bobbin casing relative to the machine frame in order that the needle thread loop may be carried around the bobbin casing and be withdrawn through the space provided by the play. This particular construction is old and well-known and has not been illustrated in complete detail herein. The bobbin casing is provided with a rib S0 which is received in an annular grove S2 formed in the recessed portion 84 of the rotary hook 82. In general, the annular groove 92 is formed in the body of the hook 82 as shown at the upper portion of Fig. 3. However, it will be observed that at the lower portion of Fig. 3 two walls of the groove 92 are formed in the hook body while the third wall is defined by an inwardly turned flange 94 formed on a detachable part 95 of the hook mechanism which part is secured to the hook body as by screws 98.

It will be apparent that since the bobbin casing 83 is held substantially against rotation and the hook body B2 is driven for rotation at an extremely high speed, the rib and groove 92 comprise interengaging bearing parts which must be carefully lubricated. It is also apparent that to avoid Contact of oil with the thread an excessive quantity of oil cannot be used for lubrication of such bearing. It is known to form the rotary hook shaft with a longitudinal bore therein through which oil may be conducted to the hook body. It is also known to form suitable passageways within the hook body through which oil discharged by the bore in the hook shaft may be thrown by centrifugal force into contact with the bearing surfaces of the interengaging hook and bobbin parts. The present invention is directed to a new and improved structure for the positive supply of oil to the hook shaft bore.

To this end there is mounted in the web portion l2 of the casting, as seen in Fig. 2, a bushing |00 through which the shaft 33 extends. The bushing |06 extends to the right, as viewed in Fig. 2, beyond the web portion l2 and has formed on the exterior surface thereof threads |02 for receiving an internally threaded packing gland Itri within which is positioned suitable packing material |05.

As shown in Fig. 5, an opening |08 is formed in the web portion 12 and extends inwardly thereof into communication with vertically disposed aligned openings H0 and ||2 in the web portion l2 and the bushing |00 respectively. The opening ||2 communicates with an annular recess Il formed in the bushing |00 and extending around the shaft 38. A second annular recess I l5 is formed in the bushing |00 in horizontal spaced relationship with the annular recess H4. The portion of the shaft 3S extending between the recesses H4 and H6 has formed therein a continuous spiral groove i |8. The spiral groove ||8 .is inclined in such direction that upon rotation of the shaft 38 in its normal direction in operation of the machine, the spiral groove ||8 will carry oil from the recess ||4 to the recess IIB.

In the machine shown in the drawings the spiral groove i3 is cut as a right-hand thread would be cut and the shaft 38 normally revolves in a counterclockwise direction as viewed from the lefthand end of Fig. 5.

Referring next to Fig. 2, the annular recess I6 communicates with a horizontally disposed passageway |20 formed in the bushing |00 which in turn communicates with a horizontally disposed passageway |22 formed in the web portion 12.

lhe;y passageway f |22 includes an 'enlarged portion Within, which is` positioned .a hardened needle valveiseat; |24 the outer end vof which opens` into afreeessll in the web portion lf2. A needlev|25 isprojected; through a suitable opening in the base casting and web portion 'lintooperative relatiorishipl with thev needle valve seat |24. The outer end oi' theneedle tt is threaded as at |28 into the base castingand is Supplied withasutably indexed operating, knob. its; and a. lock: nut |;3 2 Ruta-tion of; the adjusting knob |31) isefgfectiveto vary the relationship of the needle |28 the needle valve seat |24 and .thegneedle may-belocked in adjusted position by tighteninggthe lock nut |32 against the frame. of `the mahllvef The recess |21 comprises a continuation ofthe bQle in web portion 'l2 which receives bushingV lll and is closedat its right-hand end as viewed iny Fig. 2 by a suitable threaded plug |34.

The hook shaft 53 is provided with a central bore- |3-5 extending throughout the lengththereof. The-.left-hand end of the bore terminates in the headi and 'preferebly.Y is. flared; outwardly. as; indicated at |38. As shown in Fig. 3, the dared opening |38 communicates with a pocket or recess |150 in the body of the rotary hookv 82. Asamatter of convenience, the recess Itl may comprise merely an extension of the opening which reeeives'the head` Sil of the hook shaft.

The recess |89; thus provided may be closed by a d isc- Mzseated in a recess Idil in theA hook body in such manner .that the outer surface, of the discy |62 isv ilushwith the surface of the recess M withfin which the, bobbin casing is carried. It has been found, to be particularly desirable vin connection with; the present invention to provide the disc |132 with a central opening |45 aligned with the bore |36 of they hook shaft. The opening |56 serves as an air ventto prevent the-system from becoming air-bound. There is no danger of oil escaping through the vent |43 in view-of the fact that the hook body rotates at-a very high speed andthe quantity o f oilnorinallysupplied issufc-ient only to forma moving of; oil heldby centrifugalforce against vthe innercylindrical surface of the annular recess |46.

The body of the hook t2 has formed therein a radially-disposed,passageway |63 the outer end ofywhichf is closed by a plug |55), The passageway Ifll` communicates with a generally horizQntally-disposed passageway |52 extending into the annular recess 92 within which the rib 95 of the bobbin casing is carried. Obviously, a pluralitvof radial passageways |63 may beprovided, if so desired.` There is thus defined a contliuous oil;passageway extending from the spiral pump mechanism on thevshaft 38 to the interengaging surface 9B, 92 of the bobbin casing and rotary,v hook, respectively.

. As. shown in Fig. l, two oil sumpsare provided in the lower portion of the base of the machine. The main oilisump is indioatedat |54 andex-l tendsfromthe rear kWall i5 of the machine vto the fronty Wall |16 thereof. Referring briey to Figi v2, the main sump |511 will be observed to extend transversely .ofthe machine throughout its entire width. A sight gauge |56 having markingsiand I5? is shown inFigsz andi. The gaugeA |55... extends into themain-oil' `sump-for thepurpose of visually indicating the'levelof voil therein. Preferably the gauge |56 is made-of ra transparent materiales disclosedin U. S. Patent 6i No.' 2*;30'19460-granted November 10 ,u t942ztoaSauer.' A- hook shaft oil sump |58: is'. defined betweenathe Webxzportions 4.2 and .'l2l andlv suitable web.:po`r; tions l-zandiillasseen.inFig. '4. .Theysump` het is closed;k at the bottom by; means of a. cover plate..Iemand-gasket |65. A sight, gauge |58: similar to the. gauge. |55 extends, into .the voil sumpliandistprovided with. markings |10 and` |i'lf2 indicating respectivelythe .upper and lower? limits between-which the level. of oilpshould` be maintained. As shown in 4liigwi and inFig; l', thew level. of i oil'. in the` hook. shaft :sump |5131Will ordinarilyf substantially submerge the portion of; the shaftraf extending through the 'sump |58. Thusefthe level off oil:- is well`v above thei opening Iiias willjbeapparent. in. Figs.- 4- and 5.y The :static headl-.onthe 'bodybf oil in .the;sumpz|;58= will. therefore insure that oil will lowxthrough thewpassageviay |0811Jand risel Wellinto, the annular. recess.` |;|-4;rcommimicating therewith., Ro.- tation of the shaft 38 and the action of the spiral. groove ||8 will be effective to draw oil; from; the annular` recess'V t; and discharge itV into the annular'recess |116. Thepaching gland lildfisppro.-

. vided forl thepurpose of.preventingl the escape of; oil along; the shafty 3 8.

@il inrtheannular recess ||6 will be discharged through-.thepassageway. |21! (in Eig. 2) and; past theneedle valve |274, |2v. The quantity.. of; oil passing@ the .needle valveI and: the, pressurezde: veioped will; bev dependent upon the adjustment ofthe needle valve. The oilvpassingY-thevneedle valve. Mi, |2,6. willentertherecess |21 andv from this ,recess- J will flow into.L the bore ISB-.of .the retaryfhcekashaft.

Inyvietv orf-*they speed of rotation-of the hook shaft-.oilsuppliedfto theborel |36 bythe pumping mechanism, just, described will be distributedas acontlnupus `1"ilni ov,e1gthe entire surfaceof the bore. The film` of oil 1 will achieve an average thickness:depending-upon the rate-at which oil issupplied fromthe spiralpump. As oil'issupplied at the right-hand end of the bore, acorresponding -amountwill be caused to leave the left-hand; end of thebore and to enter .thehook budy, 82. Itwill bel appreciated, therefore, .that thea-ate` at `which oil issupplied to the hook body-may be vervaccurately controlledloy manip:- ula-ticn of the needle valve.|24, |26. When `the machine is stopped, there will be substantially no tendency. for .oil to continue flowing into the hook body .82.l This is aA particularlyY importantfeature ofc the invention inasmuch as many previous vmechanisms.involving gravity or Wick ieeds for thelubrication of the rotaryhook havehadthe tendency. to ,continue the iiow of oilafter themachine is; stopped. Such continuedfow Willplace excess oilinthe hook body where it is likely to bethrownnpon the work immediately that the machineis re-started. At the same time a small amountof oil remains distributed throughout the length ofthe Shaft, in accordance with thisinvention, andjsuch oil is instantaneously available lfor delivery to thehook raceway as soon asjthe machine is 1re-started. Such. delivery is Vl'uought about' through thev centrifugal' pumping action produced bythesloping surface |38 and the vradial duct |48. g

The arrangement of the spiral pump on the drive shaft 33 and the` provision of direct passageways from the pump to the inner end of the hook shaft offers the distinct advantage that the pump is driven avt-a speed of rotation only onehalf l'thatof the hook shaft; Since avery small quantity of" oil is-requiredV it is decidedly advantageous to make use of a relatively low-speed pump capable of moving an adequate quantity of oil under a relatively low pressure. With such an arrangement the adjustment of the needle valve |24, 126 is not unduly critical. When it is desired to flush the hook, it is necessary only to open the needle valve rather widely for a brief period and then to readjust it to normal position as indicated by the indexed knob |30. The excess oil will soon be thrown from the hook andnormal operation may be resumed.

From the above detailed description it will be apparent that I have provided a mechanism which accomplishes the objects of the invention.

While an illustrative form of the invention has been disclosed in considerable detail, it will be understood that various changes may be made in the construction and arrangement of the several parts without departing from the general principles and scope of the invention as defined in the appended claims.

I claim:

1. In a sewing machine, the combination of a frame, a rotary hook, a rotary hook shaft, a rotary drive shaft, means connecting said drive shaft with said hook shaft for rotation of said hook, a stationary bobbin casing supported in said hook, said hook and casing having cooperating bearing surfaces requiring lubrication, means within said hook for directing lubricant from a point adjacent the axis of said rotary hook shaft to said bearing surfaces, said rotary hook shaft having a passageway extending axially thereof, means in said frame having a recess therein communicating with the end of said passageway remote from said hook, a rotary pump on said drive shaft, a lubricant reservoir communicating with the intake of said pump, means for directing lubricant from the discharge side of said rotary pump to said recess, an adjustable needle valve interposed between said pump and said recess, and means for indicating the position of adjustment of said needle valve.

2. In a sewing machine, the combination of a frame, a rotary hook, a rotary hook shaft, a rotary drive shaft, means connecting said drive shaft with said hook shaft for rotation of said hook, a stationary bobbin casing supported in said hook, said hook and casing having cooperating bearing surfaces requiring lubrication, means within said hook for directing lubricant from a point adjacent the axis of said rotary hook shaft to said bearing surfaces, said rotary hook shaft having a passageway extending axially thereof, means in said frame having a recess therein communicating with the end of said passageway remote i'rom said hook, a rotary pump on said drive shaft, a lubricant reservoir communicating with the intake of said pump, means for directing lubricant from the discharge side of said rotary pump to said recess, an adjustable needle valve interposed between said pump and said recess, and a knob exterior of said frame for adjustment of said needle valve, said knob having index marks thereon for indicating the position of adjustment of said needle valve.

3. In a sewing machine, the combination of a horizontal-axis rotary hook, a horizontal-axis rotary hook shaft, a horizontal-axis drive shaft, means connecting said drive shaft with said hook shaft for rotation of the latter, a stationary bobbin casing supported in said hook, said hook and casing having cooperating bearing surfaces re quirng lubrication, means within said rotary hook for directing lubricant from a point adja cent the axis of said rotary hook shaft to said bearing surfaces, a passageway extending axially cf said rotary hook shaft, and means for supplying lubricant to said passageway, said last-named means comprising a spiral pump carried by said drive shaft, a reservoir for containing a supply of lubricant exclusively for said bearing surfaces, a passageway connecting said reservoir with the intake side of said spiral pump, a discharge passageway from the discharge side of said pump, and an adjustable needle valve associated with said discharge passageway for regulating the quantity of lubricant discharged by said pump into the passageway in said rotary hook shaft.

4. In a sewing machine, the combination of a -rotary hoo-k, a rotary hook shaft, a drive shaft alongside said hook shaft, means connecting said drive shaft with said hook shaft for rotation of the latter, a stationary bobbin casing supported in said hook, said hook and casing having ccoperating bearing surfaces requiring lubrication, means within said rotary hook for directing lubricant from a point adjacent the axis of said rotary hook to said bearing surfaces, a passageway extending axially of said rotary hook shaft, and means for supplying lubricant to said passageway, said last-named means comprising a spiral groove formed in a portion of said drive shaft closely adjacent to said hook shaft, a bushing surrounding said drive shaft in the region of said spiral groove, said bushing having an annular recess therein communicating with a supply of oil and said recess being positioned at one end of said spiral groove, a second annular recess formed in said bushing adjacent the 0pposite end of said spiral groove, means for rotating said driveshaft in a direction such that said spiral groove will conduct oil from said rstnamed recess to said second-named recess, a discharge passageway communicating with said second-named recess, an adjustable needle valve associated with said discharge passageway for controlling the amount of lubricant emerging from said discharge passageway, and means for directing the lubricant thus discharged into the passageway formed in said rotary hook shaft.

5. In a sewing machine, the combination of a rotary hook, a horizontal-axis rotary hook shaft, a horizontal-axis drive shaft alongside said hook shaft, means connecting said drive shaft with said hook shaft for rotation of the latter at a. substantially greater speed than that of said drive shaft, a stationary bobbin casing supported in said hook, said hook and casing having cooperating bearing surfaces requiring lubrication, means within said rotary hook for directing 1ubricant from a point adjacent the axis of said rotary hook to said bearing surfaces, a passageway extending axially of said rotary hook shaft, and means for supplying lubricant to said passageway, said last-named means comprising a spiral groove farmed in a portion of said drive shaft closely adjacent said hook shaft, a bushing surrounding said drive shaft in the region of said spiral groove, said bushing having an annular recess therein communicating with a supply of oil and said recess being positioned at one end of said spiral groove, a second annular recess formed in said bushing adjacent the opposite end of said spiral groove, means for rotating said drive shaft in a direction such that said spiral groove will conduct oil from said first-named recess to said second-named recess, a discharge passageway communicating with said second-named recess, an adjustable needle valve associated with said discharge passageway for controlling the amountl of lubricant emerging from said discharge passageway, and means for directing the lubricant thus discharged into the passageway formed in said rotary hook shaft.

6. In a sewing machine, the combination of a rotary hook, a rotary hook shaft having a passageway extending axially thereof, a drive shaft alongside said rotary hook shaft, means for rotating said drive shaft, means connecting said drive shaft with said rotary hook for rotation of said rotary hook shaft at a higher speed than that of said drive shaft, a spiral pump on a portion of said drive shaft closely adjacent to said rotary hook shaft, means including a passageway having an adjustable needle valve therein for conducting lubricant from said pump to the axial passageway in said rotary hook shaft, a stationary bobbin casing supported by said hook, said hook and casing having cooperating bearing surfaces requiring lubrication, said rotary hook having a recess communicating with the passageway in said rotary hook shaft, and means in said rotary hook for directing lubricant from said recess to said bearing surfaces.

7. In a sewing machine the combination of a frame, a rotary hook, a rotary hook shaft having a longitudinal passageway extending along the axis thereof, a drive shaft alongside said rotary hook shaft, a frame member interposed between said rotary hook shaft and said drive shaft, a reservoir for containing lubricant exclusively for said hook, said reservoir having generally vertical sidewalls and a bottom, one of said sidewalls comprising said frame member, said drive shaft 10 extending through said reservoir, a spiral pump on said drive shaft, means defining a recess at the intake end of said spiral pump and a passageway connecting said recess with said reservoir, means defining a second recess at the discharge end of said spiral pump, means defining a third recess at the end of said rotary hook shaft opposite said hook, said second recess and said third recess being located on opposite sides of said frame member and being substantially opposed to one another, said frame member having a passageway extending therethrough and connecting said secc-nd recess and said third recess, and an adjustable needle valve located in said last-named passageway to restrict the area thereof to adjustable extents whereby to permit the flow of varying quantities of lubricant under pressure from Said spiral pump to said longitudinal passageway in said rotary hook shaft.

GEORGE SAUER.

REFERENCES CITED The following references are of record in the nie of this patent:

UNITED STATES PATENTS Number Name Date 1,746,055 Roberts et al. Feb. 4, 1930 2,112,172 Mackay, Jr. Mar. 22, 1938 2,128,573 Myers Aug. 30, 1938 2,151,338 Zonis Mar. 21, 1939 2,209,338 lsessler July 39, 1940 2,283,869 Graesser May 19, 1942 2,284,474 Peets et al May 26, 1942 2,300,388 Parry Oct. 27, 1942 2,318,447 Zonis et al. May 4, 1943 2,383,152 Parry Aug. 21, 1945 

